This application claims the priority of German patent document DE 10 2005 020 818.5, filed Apr. 5, 2004 and German patent document DE 10 2005 020 817.7, filed Apr. 5, 2004, the disclosures of which are expressly incorporated by reference herein.
The present invention relates to a method for operating an electrically adjustable vehicle seat.
German patent document DE 199 34 472 A1 discloses a vehicle seat with adjustable contours and a backrest having air cushions arranged one on top of the other for forming a contour for the hollow of the back. A control device is provided for controlling the inflation pressure in the air cushions, and an operator control unit is connected to the control device for setting the inflation pressure.
German patent document DE 42 37 072 C1 describes a resistive film pressure sensor which is embodied as a sensor mat for detecting the occupation of a seat. The film pressure sensor outputs an analog signal which is indicative of the normal force which acts on its surface, and can be used to form a rough interrogation of the weight resting on the seat. It is thus possible to define a lower limiting value below which triggering of an airbag is suppressed. (It is assumed that when the weight is less than the limiting value the seat is not occupied.)
Furthermore, German patent document DE 100 11 372 A1 discloses a sitting weight measuring device for measuring the sitting weight on a vehicle seat, the sitting weight also including the weight of a vehicle occupant sitting on the vehicle seat. The sitting weight measuring device has a plurality of load cells with a multiplicity of sensors, each sensor of which converts at least part of the sitting weight into an electrical signal. The load cells are inserted in a region between the vehicle seat and the seat attachment sections of a vehicle bodywork. In addition to the weight of the vehicle occupant, the sitting weight measuring device can also determine the distribution of the weight of the vehicle occupant over the vehicle seat. With a knowledge of the weight and distribution of the weight, it is possible to actuate safety devices, in particular airbags and seatbelts, in such a way that optimum protection in terms of safety technology is ensured for the vehicle occupant.
Finally, German patent document DE 102 49 960 A1 discloses an OC (Occupant Classification) system which is based on the dependence between bodyweight and the distance between the hips of a seat occupant. For this suppose a so-called OC mat evaluates the pressure profile on the sitting area on the basis of its installation location in a vehicle seat and its physical method of operation. Analysis of the measured pressure profile permits an unoccupied or an occupied seat to be detected. When the seat is determined to be occupied, a distinction is then made between a person and a child's seat or similar object, based on the sitting profile of the person, or an impression which is typical of a specific object. When a person is detected, he or she is further classified with regard to various classes which correspond to the size of the body and to the bodyweight.
One object of the invention is to provide a method for operating an electrically adjustable vehicle seat which has at least one electrically adjustable upholstered seat element and a sitting weight measuring device for sensing the weight of a vehicle occupant sitting on the vehicle seat, and which senses the weight of the vehicle occupant with a high degree of measuring accuracy.
Another object of the invention is to provide a method for setting parameters for operating such a vehicle seat with a weight measuring system, which method provides an increased degree of safety relative to the prior art, in a driving mode, and particularly in a hazardous situation.
These and other objects and advantage are achieved by the method according to the invention, in which, for an initial sensing of the weight by the sitting weight measuring device, the upholstered seat element of the electrically adjustable vehicle seat is automatically moved into a measuring position. The vehicle seat in this instance has at least one electrically adjustable upholstered seat element which includes an inflatable air cushion, a seat cushion lowering means, a side support or thigh rest, and a sitting weight measuring device for sensing the weight of the vehicle occupant sitting on the vehicle seat. The adjustable upholstered seat element can be used, for example, to form a control for the hollow of the back, (such a seat being referred to in this configuration as a multi-contour seat), to implement a massage mode or to set the hardness of the seat.
Activated adjustable upholstered seat elements of the vehicle seat, which make available a so-called comfort function, can considerably influence the result of the sensing of the weight and falsify it. For example, the vehicle occupant's weight which is sensed with the sitting weight measuring device can be less than the actual weight of the vehicle occupant if parts of the body of the vehicle occupant are supported by the adjustable upholstered seat element so that the entire actual weight of the vehicle occupant is not sensed by the sitting weight measuring device. If actuation of the comfort function for the multi-contour seat is restricted during the sensing of the weight, more precise sensing of the weight can take place.
Preferably, in the measuring position, the upholstered seat element acts on the vehicle occupant to only a restricted degree, or not at all. That is, the comfort function for the vehicle seat is at least partially deactivated in this configuration. As a result, it is possible to sense reproducible values for the weight of the vehicle occupant which correspond to his or her actual weight. Subsequent adjustment of the upholstered seat element can take place on an individual basis, as a function of the actual weight of the vehicle occupant. As a result of the increased measuring accuracy for the sensing of the weight it is possible to increase considerably both the comfort and safety for the vehicle occupant. Furthermore, incorrect triggering of safety systems connected downstream (for example, an airbag system which is assigned to the vehicle seat) is thus very largely avoided.
The sitting weight measuring device can comprise, in particular, a sensor mat which can be integrated into the vehicle seat with a low degree of technical complexity. The sensor mat can contain, for example, resistive film pressure sensors. However, it is also possible to use other weight pickups for sensing the weight, for example load cells.
Preferably, initial weight sensing takes place within a provided time interval after the opening of a door of the motor vehicle (which is sensed by means of a door contact switch), or after occupation of the seat has been detected. As a result, early sensing of the weight is ensured and more wide ranging weight-dependent measures for increasing the comfort and the safety of the vehicle occupant can be initiated even before the journey starts.
In one configuration of the invention, an adjustment range of the electrically adjustable vehicle seat, or of the upholstered seat element, is predefined as a function of the current value of the sensing of the weight. (The electrically adjustable vehicle seat comprises at least one electrically adjustable upholstered seat element, an inflatable airbag, a seat cushion lowering means, a side support or a thigh rest, and the weight sensing system for sensing the weight of a vehicle occupant sitting on the vehicle seat.) The vehicle occupant is provided with an adjustment range for the upholstered seat element, which is suitable in terms of comfort and safety (for example in terms of medical and ergonomic criteria), which range is adapted individually to his currently sensed weight. The adjustable upholstered seat element may be used, for example, for forming a contour of the hollow of the back, for implementing a massage mode or for setting the hardness of the seat.
The sensing of the weight may be implemented, for example, by means of an Occupant Classification system or a sitting weight measuring system. For the purpose of restricting the adjustment range, indirectly measuring weight sensing systems (for example optical vehicle occupant sensing systems) which also permit conclusions to be drawn about the weight of the vehicle occupant, are also conceivable. A means of adjusting the upholstered seat element can be activated by the vehicle occupant or automatically, as can the comfort function.
In one refinement of the invention, the value range for weight sensing is divided into weight classes, and an individual adjustment range for the upholstered seat element is predefined for each weight class. It is possible, for example, to define a weight class for vehicle occupants with a high weight, a medium weight and a low weight, permitting persons to be classified and sorted according to their weight. A weight class comprises, for example, small children with a child's seat and children, and a further class comprises women with a low weight. The adjustment range of the upholstered seat element is adapted in an optimum way in terms of safety technology to each weight class. When control is carried out, a large group of vehicle occupants can thus be provided with the entire adjustment range of the upholstered seat element. The adjustment range, the so-called comfort range, is correspondingly limited for a small group of vehicle occupants which comprises, in particular vehicle occupants with a very low weight or a very high weight. In this context it is advantageous if a lower weight sensing threshold value above which the upholstered seat element can be adjusted is predefined.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.